For protein delivery, it is desirable to load polymeric nanoparticles and microparticles with proteins. Typically, a protein may be adsorbed on the particle surface or be entrapped within the particle matrix. During the initial phase of protein release or delivery, proteins adsorbed on to the surface may release in an initial burst followed by a slower release phase due to the diffusion of entrapped protein. The protein may also be released from the particles if the constituent polymer is erodible and/or biodegradable. Such polymers, however, face challenges including among others with regard to a high burst release, unpredictable behavior in the later stages of biphasic release profile, overall drug release kinetics, stability during processing, and preservation of the biological activity of the released protein.